MELBOURNE — Ukrainian teen Dayana Yastremska idolized Serena Williams from the time she picked up a racket when she was 5.

When watching Williams play on TV as a child, she imagined she was helping the former world No. 1 to win her matches. She also dreamed of a day when she might play Williams in a big match at a big arena.

That day came on Saturday at the Australian Open when the two played a third-round encounter on Rod Laver Arena.

That was where, at least when it came to the tennis, the 18-year-old Yastremska’s dream turned into a nightmare as Williams offered her a precise 6-2, 6-1 tennis lesson in all of 67 minutes.

While Williams, 37, was marshaling a path to the fourth round without even facing a break point, Yastremska was seen sitting courtside at the changeovers shrugging her shoulders at her team.

After Yastremska, serving, hit a backhand crosscourt way wide on a second match point, the two met at the net. Williams, channeling her maternal compassion, immediately told Yastremska, “You were amazing,” but the Ukrainian bit her lip as she fought back tears. Williams then told her “don’t cry” and the two hugged.

“I thought she was amazing,” said Williams, when on-court announcer Sam Smith mentioned Yastremska appeared intimidated. “She came out swinging.”

Later, Williams said she believes Yastremska's post-defeat reaction was actually a great positive.

“As she was walking towards the net, I could tell she was quite upset,” Williams said. “I kind of liked that. It shows she wasn’t just there to play a good match, she was there to win. She wanted to win. That really broke my heart.

When asked if she ever experienced that reaction when playing a match in her teens, Williams said she did as a younger player and as an adult.

“Absolutely,” she said. “You go out there and you want to win. I remember one time in particular against Venus at Wimbledon, as I was walking to the net, I started bawling. I couldn’t help it.”

Yastremska, who was born months after Williams won the first of 23 Grand Slam trophies at the 1999 US Open, doesn’t yet have the weapons or mind-set to challenge a player of Williams’ merit. She was playing only her fourth main draw Grand Slam match, while Williams was playing her 379th and now has a 334-45 record at the majors.

Williams is hoping to win an eighth Australian Open title, which would enable her to tie Australian Margaret Court’s record of 24 Grand Slam singles titles.

At 4-1 in the second set, Yastremska had the trainer on court after she turned over her right ankle in the previous game.